/usr/share/doc/ is in libportmidi-dev 1:200-0ubuntu3.
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/usr/share/doc/libportmidi-dev/
/usr/share/doc/libportmidi-dev/README.txt
/usr/share/doc/libportmidi-dev/copyright
/usr/share/doc/libportmidi-dev/examples/
/usr/share/doc/libportmidi-dev/examples/midithru.c
/usr/share/doc/libportmidi-dev/examples/sysex.c
/usr/share/doc/libportmidi-dev/examples/pminternal.h
/usr/share/doc/libportmidi-dev/examples/Makefile
/usr/share/doc/libportmidi-dev/examples/mm.c
/usr/share/doc/libportmidi-dev/examples/midithread.c
/usr/share/doc/libportmidi-dev/examples/pmutil.h
/usr/share/doc/libportmidi-dev/examples/qtest.c
/usr/share/doc/libportmidi-dev/examples/test.c
/usr/share/doc/libportmidi-dev/examples/latency.c
/usr/share/doc/libportmidi-dev/examples/midiclock.c
/usr/share/doc/libportmidi-dev/README_LINUX.txt
/usr/share/doc/libportmidi-dev/changelog.Debian.gz